This study assessed the safety, tolerance, and activity of a single dosage combination of ZDV and ddC versus ZDV and placebo in clinically stable HIV-1 infected children age 3 month to 12 years who have previously been treated with AZT alone. The study addressed whether the combination of ZDV and ddC offered advantages in tolerance or clinical efficacy compared to monotherapy with ZDV. Children were closely monitored for neurotoxicity. This study has not been completely analyzed.